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Anosmia

Mohammed alqabasani R 5

Rhinology research chair academic activity

13-11-2013

King saud university

[email protected]

Rhinology Chair

Rhinology research Chair Weekly Activity

The chemo senses of smell and taste contribute to quality of life and environmental appreciation they also play significant role nutrition and safety.

Disorders of olfaction are common worldwide and may involve as many as 2 to 4 million people in the United States

anatomy

► the nasal passages

contain the structures of olfaction which include:

► the upper nasal septum , middle and superiorturbinates.

► These structures facilitate airflow and contain the primary olfactory neurons

anatomy

► In the olfactory mucosa,

the axons from the bipolar olfactory neurons coalesce

into bundles to form cranial nerve I

This nerve traverses upward through the cribriform

plate and skull base to the olfactory bulb to cortex

histology

►The olfactory epithelium is primarily composed of pseudostratified columnar-type epithelium

situated with a vascular lamina propria, and lack a submucosa.

► It is derived from ectoderm

► It can regenerate after damage but it rarely complete also it depend on degree of damage

histology

Histology

►The human olfactory epithelium covers an area of roughly 1 cm2 on each side

► Humans have approximately 6 million olfactory neurons each cell express single odorant receptor

histology

►The cells that facilitate olfaction are divided into 4 main cell types:

1-ciliated olfactory receptors.

2-microvillar cells.

3-sustentacular cells.

4- basal cells.

Nerves involve in smell

►Cranial nerve I mediates the olfactory response

►The trigeminal nerve relays irritating odors such as carbon dioxide and ammonia

►Cranial nerves IX and X assist in retronasal olfaction

►Most patient-described losses or

disturbances of taste are olfactory losses.

►True solitary taste loss is less common

Taste

► Grossly, the tongue is composed of multiple taste papillae geographically distributed:

Fungiform,circumvallate and foliate

papillae which contain taste

buds that facilitate gustatory sensation

► The filiform papillas do not contribute to taste

PHYSIOLOGY OF SMELL

► Nasal airflow plays an integral part of smell detection.

► As airflow distributes itself in the nasal cavity, about 15% flows to the olfactory cleft

PHYSIOLOGY OF SMELL

► key to this process is that odorant

molecules must dissolve in or pass through the

mucous overlying the olfactory epithelium to be

detected. Once the odorants bind to the receptor

neurons, a complex enzyme-mediated pathway

Will start

PHYSIOLOGY OF SMELL

PHYSIOLOGY OF TASTE

► In the taste buds, the chemical

molecules are transformed into electrical signals

that travel to the nucleus solitarius (medulla), to

the ventricular posterior medial nucleus in the thalamus then to the parietal lobe, and give the

perception of gustation

PHYSIOLOGY OF TASTE

► olfaction and food flavor perception is

retronasal olfaction, which occurs during

ingestion of substances with airflow of

odorant molecules generated by exhalation

or mouth and pharynx contraction.

DIAGNOSIS AND WORKUP OF OLFACTORYloss

► Hyposmia describes a decreased ability to

perceive smell

► Anosmia describes the absence of useful

smelling ability

► Parosmia is the distorted perception of

odor following a stimulus

► Phantosmia is perception of odor in the

absence of an odorant stimulus.


►History:

►age

►the onset, sudden vs gradual ,

►Side and duration of smell and taste changes.

►The patient may not disclose an olfactory disturbance unless directly asked.


►Any nasal symptoms should be addressed in details

►Associated clinical clues such as preceding trauma or viral infection ,exposure to toxin smoking

►Taste loss vs flavor


►Past surgical history:

Any nasal surgery

►Past medical: radiation ,delayed puberty ,dementia and neurological disease

►Detailed medication history

►Family history of anosmia

Physical Examination for Olfaction

► Complete head and neck examination with specific concentration on:

anterior rhinoscopy may reveal gross disease such as septal perforation, polyps, and epistaxis, tumors, or allergic edematous nasal mucosa

► nasal endoscopy, a view of the olfactory cleft and assessment of blockage

► Neurologic status and cranial nerve functionshould be assessed

► Documentation of the physical examination is vital beforesurgery.

Olfactory testing

►Is it important ? why ?

►1-to establish validity &nature of patient complaint

►2-to monitor the changes over time

►3-to detect malingering

►4-establish compensation for permanent disability

Investigation of anosmia

►Two classes of testing are available:

electro physical and psychophysical tests however psychophysical tests are more useful in the interoffice setting, more widely used.

►Olfactory testing generally measures either threshold of smell or identification of various smells

psychophysical tests


►Mostly common used test is UOPSIT (smell identification test ):

►Easy test can be finished in 15 minutes multiple language

►It has four booklets contain 10 odorant

►Stimuli are embedded 10-50 micro m diameter encapsulated crystals located on scratch and sniff strip


►UOPSIT (smell identification test ):► Over each strip mcq with four choices patient should choose answer even if

none seems appropriate or no odor perceived

► Then patient classified according their score to six groups :normosmia ,mild ,moderet, sever micosmia ,anosmia and malingering

► because chance performance is 10 out of 40 reflect avoidance which detect malingering patient


►Electrophysiological test

►1-odor event-related potential (OERPs):Which measure EEG from scalp electrode following presentation of odorant

It is good to detect malingering patient but can not be standardized

►Electro-olfactogram (EOG):Electrode inserted in olfactory cleft which measure the action potential it is no

good because of the difficulty in doing the test and its not reliable

Investigation

►Neuropsychological tests :

There is association between anosmia and neurodegenerative disease like Alzheimer's, dementia and Parkinson

So mini-mental state examination is easy screening tool if abnormal better to send the patient to neurologist for further assessment


► the history, physical examination, or olfactorytests suggest polypoid or obstructive disease ormalignant potential, then sinonasal imaging isComputed tomography (CT) scans of pns is needed

►Magnetic resonance imaging (MRI):may visualize the olfactory sulci and brainstructure

Common Causes of Olfactory Loss

►Olfactory disturbances can be

better separated into those with a conductive

component (anatomic blockage of the olfactory

cleft or surrounding structures) and a sensorineural

component (a nerve loss or damage to receptor

or higher cortical processing).


►Nasal inflammatory disease:

nasal disorders from chronic rhinosinusitis to

polyps or allergic edema.

This group of disorders

is thought to primarily alter nasal airflow to the olfactory cleft


► After Upper Respiratory Infection:

► Many patients report temporary decreased smell during upper respiratory infection (URTI) The nasal membrane edema commonly abates within a few days and smell returns to baseline.

However in a subset of patients, there is permanent loss and the prognosis is principally poor, with only one-third recovering

► In these patients a sensorineural insult occurs to

the primary olfactory neurons more in female

Causes of Olfactory Loss

►Head Trauma and Loss of Smell

► About 5% to 10% of patients with head trauma

suffer from smell loss, often from occipital or

frontal blows of the cribriform plate injury to the

olfactory bulb,or supraorbital and frontal brain

contusions that result in axonal injury.


►Aging and Loss of Smell

sense of smell has been studied and defined

with age-related norms and known decreases

especially in individuals more than 65 years of age.


►Congenital Loss of SmellThe cause is secondary to degeneration or failure of formation of the

olfactory bulb and/or epithelium during development

These patients often present around 8 years

► Kallman syndrome or hypogonadotropic

Hypogonadism the most common one


►Toxins and Loss of Smellis best described as a sensorineuralInjury

It representbetween 1% and 5% of olfactory Disorders

The diagnosis is largely based o history and known

environmental exposure to the toxin.


►Neoplasm and Loss of Smell

intracranial meningiomas, gliomas, and other

tumors may cause confined destruction of the

central olfactory neurons.

The intranasal tumors most frequently encountered are inverting papillomas, adenomas, squamous cell

carcinomasand esthesioneuroblastomas.


► Postsurgery Loss of Smell:

If surgeons do not test and document olfactory loss at baseline they can miss a loss before surgery

Mechanism for loss post surgical intervention:► 1. Scar tissue► 2. Granulation tissue► 3. Persistent mucosal edema► 4. Inflammation and olfactory neuroepithelialdamage

Postsurgery Loss of Smell

►Middle turbinate resectionKimmelman1 suggested that a resection of thelower half of the middle turbinate likely doesnot result in anosmia or hyposmia

► study completed by Biedlingmaierand colleagues82 reviewed patients with partialmiddle turbinate resections during routine sinussurgery. They found that only 1 patient outof 198 (0.9%) complained of anosmia


► Septoplasty complications:

Overall, olfactory dysfunction after surgery is rare

after septoplasty One study found that total

anosmia following septoplasty in the long term

was found in 0.3% to 2.9% and hyposmia 1%.

► However, olfactory disturbance may be present

in up to 8% of patients before septoplasty, and

both the surgeon and patient may be unaware

without preoperative testing.


►Rhinoplasty complications:

Smell dysfunction following rhinoplasty has been reported and studied

► This suggests a low risk overall

(3%), but that it is nonetheless a risk that needs to be addressed with patients.


Skull base surgery and loss of smell:

Complex anterior and middle fossa skull base

surgery and many cranial surgeries near the

olfactory bulbs may cause olfactory loss


► Neurodegenerative Disorders and Loss of Smell:

Much research has recently been devoted to the link between olfactory loss and neurodegenerative disorders such as Alzheimer disease and Parkinson Disease

Psychiatric Disorders (Depression or Anxiety)and Loss of Smell

TREATMENT OF OLFACTORY LOSS

►A patient’s quality of life is affected after an olfactory loss, from enjoying a meal to safety around toxic chemicals

►Determining the cause of the olfactory

deficit is imperative in counseling the patient and

predicting the likelihood of improvement


► Sensorineural losses are less likely to recover,

Whereas conductive losses, for example obstructive

nasal polyps, are more easily treatable


► Conductive smell losses resulting in hyposmia

or anosmia after nasal surgery or obstructing

URIs have treatments available

Nasal treatments:

including saline irrigations and a nasal steroid

spray, may decrease nasal membrane edema,

increase nasal airflow, and improve olfaction


► Medicines such as high

dose oral steroid boluses tapered over 3 weeks

have been studied with promising results.

recent study noted that a systemic steroid administration is

useful in distinguishing betweena conductive loss that will

improve and a sensorineuralloss that will not respond


►training the hyposmic or anosmic

patient to appreciate remaining sensory

modalities such as texture of food, residual

taste,and mouth feel is beneficial.


► Protection remains a critical aspect of smell Loss

Educating patients’ family members

► Patients with olfactory loss must use smoke

and natural gas detectors in their homes and offices.

► Converting to an electric powered system

may be safer.

Thank you

►Any question?

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